My ACE is a close cousin to the Vegas. Was the hose below the fresh water tank or somewhere else? My fresh water drain is on the other side of the coach, is why I asked. Make sure all of your low point drain valves are closed. In my coach they are a pull up type of valve maybe one got stuck. My ACE does not have a dedicated fresh water drain pipe. It drains through a valve in the line from tank to pump.
Or at the end of the pipe is threaded you like you said may need a plug or cap those you should be able to get at big box store. That's all I have hope it helps
Retired and never looked back